Methods, apparatuses, and circuits for programming a memory device

ABSTRACT

Subject matter described pertains to methods, apparatuses, and circuits for programming a memory device.

RELATED APPLICATIONS

The present application for patent is a continuation of U.S. patentapplication Ser. No. 15/858,780 by Redaelli et al., entitled “Methods,Apparatuses, and Circuits for Programming a Memory Device,” filed Dec.29, 2017, which is a continuation of U.S. patent application Ser. No.15/438,499 by Redaelli et al., entitled “Methods, Apparatuses, andCircuits for Programming a Memory Device,” filed Feb. 21, 2017, now U.S.Pat. No. 9,893,279, issued Feb. 13, 2018, which is a divisionalapplication of U.S. patent application Ser. No. 14/477,680 by Redaelliet al., entitled “Methods, Apparatuses, and Circuits for Programming aMemory Device,” filed Sep. 4, 2014, now U.S. Pat. No. 9,614,005, issuedApr. 4, 2017, which is a divisional application of U.S. patentapplication Ser. No. 13/218,374 by Redaelli et al., entitled “Methods,Apparatuses, and Circuits for Programming a Memory Device,” filed Aug.25, 2011, now U.S. Pat. No. 8,830,722, issued Sep. 9, 2014, assigned tothe assignee hereof, and each of which is expressly incorporated byreference in its entirety herein.

BACKGROUND

Certain types of methods and apparatuses that involve memory devices andcircuits may make use of thermal energy to bring about a change in anobservable property of a memory material within a memory device. Onoccasion, it may be useful to bring about a change in a manner toconserve thermal energy.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of claimed subject matter are illustrated by way of exampleand not by way of limitation in the figures of the accompanyingdrawings, in which:

FIG. 1 shows at least a portion of a memory device according to anembodiment of claimed subject matter;

FIG. 1A shows at least a portion of a memory device according to anembodiment of claimed subject matter;

FIG. 2 shows electrical current flow through the embodiment of FIG. 1;

FIG. 2A shows electrical current flow through the embodiment of FIG. 1A;

FIG. 3 shows a diagram of circuit elements that may represent a circuitembodiment of FIG. 1;

FIG. 4 shows a flow chart for at least part of a method of making amemory device according to an embodiment of claimed subject matter; and

FIG. 5 shows a flow chart for at least part of a method of operating amemory device according to an embodiment of claimed subject matter.

DESCRIPTION OF EMBODIMENTS

In the following detailed description, reference is made to theaccompanying figures that show, by way of illustration, specificembodiments of claimed subject matter. Embodiments are described insufficient detail to enable those skilled in the art to practice claimedsubject matter. It is to be understood that various embodiments ofclaimed subject matter, although different, are not necessarily mutuallyexclusive. For example, a particular feature, structure, orcharacteristic described herein in connection with one embodiment may beimplemented within other embodiments of claimed subject matter. Inaddition, it is to be understood that a location or arrangement ofindividual elements within a disclosed embodiment may be modified. Thefollowing detailed description is, therefore, not to be taken in alimiting sense, and subject matter for the present application isdefined by the issued claims, appropriately interpreted, along with afull range of equivalents to which the issued claims are entitled. Inthe drawings, like numerals refer to the same or similar functionalitythroughout the several views unless otherwise suggested.

Some portions of the following description are presented in terms oflogic, algorithms or symbolic representations of operations on binarystates stored within a memory of a specific apparatus or special purposecomputing device or platform. In the context of the specification, theterm “specific apparatus” or the like includes a general-purposecomputer once it is programmed to perform particular functions pursuantto instructions from program software. Algorithmic descriptions orsymbolic representations are examples of techniques used by those ofordinary skill in the data processing or related arts to convey thesubstance of their work to others skilled in the art. An algorithm ishere, and generally, considered a self-consistent sequence of operationsor similar data processing leading to a desired result. In this context,operations or processing involve physical manipulation of physicalquantities. Typically, although not necessarily, quantities may take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared, or otherwise manipulated as electronicsignals that represent information states. It has proven convenient attimes, principally for reasons of common usage, to refer to signals asbits, data, values, elements, symbols, characters, terms, numbers,numerals, information, or the like. It should be understood, however,that all of these or similar terms are to be associated with appropriatephysical quantities and are merely convenient labels. Unlessspecifically stated otherwise, as apparent from the followingdiscussion, it is appreciated that throughout the specification,discussions utilizing terms such as “processing,” “computing,”“calculating,” “determining”, “establishing”, “obtaining”,“identifying”, “selecting”, “generating”, or the like may refer toactions or processes of a specific apparatus, such as a special purposecomputer or a similar special-purpose electronic computing device. Inthe context of this specification, therefore, a special purpose computeror a similar special purpose electronic computing device is capable ofmanipulating or transforming signals, typically represented as physicalelectronic or magnetic quantities within memories, registers, or otherinformation storage devices, transmission devices, or display devices ofthe special purpose computer or similar special-purpose electroniccomputing device.

The terms “coupled” and “connected” along with their derivatives may beused. It should be understood that these terms are not intended assynonyms for each other. Rather, in particular embodiments, “connected”may be used to indicate that two or more elements are in direct physicalor electrical contact with each other. “Coupled” may be used to indicatethat two or more elements are in either direct or indirect (with otherintervening elements between them) physical or electrical contact witheach other, or that the two or more elements cooperate or interact witheach other.

Some embodiments of claimed subject matter may involve “heating,” whichmay result, at least in part, from “Joule,” “resistive,” or “ohmic”conversion of electrical current to thermal energy. Additionally,embodiments of claimed subject matter may involve a “switch” or a“switching element,” which may result from any one of numerous processesfor controlling or modulating an electrical signal. In one example, ause of a metal oxide semiconductor (MOS) transistor switch, in which asignal present on a gate of a transistor may bring about a current flowfrom a drain to a source of the transistor switch, may includeperforming a switching function. Switching may also result from acurrent flowing from a first portion of a device to a second portion ofa device triggered, at least in part, by an external signal. However,these are merely illustrative examples, and claimed subject matter isnot limited in this respect.

Embodiments of claimed subject matter may involve “dispose” or“disposing” in which a first material may be deposited over a secondmaterial, for example. In an embodiment, one or more of a variety ofchemical or metal oxide vapor deposition, sputtering, or othersemiconductor process may be used to dispose a first material over asecond material or including on a second material. Embodiments ofclaimed subject matter may involve an “etch” or “etching” process thatmay, for example, pertain to a Damascene process in which a length of aconductor may result from creating a trench and overfilling it withconductor material. Excess material may be removed using chemicalmechanical planarization (CMP), for example, to remove access materialfrom locations other than the trench.

Embodiments of claimed subject matter may involve an “active material,”such as a material comprising a phase change memory (PCM), which may,for example, undergo a reversible transition from a crystalline state toan amorphous state as a result of thermal energy imparted to thematerial. In an implementation, an active material may comprise a PCMmaterial in a crystalline state that may exhibit a lower resistance thana PCM material in an amorphous state. An active material may comprise aPCM material used as a memory cell, which may store one or moreinformation states based on, at least in part, a higher-resistance or alower-resistance state of the material. In an implementation, an activematerial may comprise a PCM material used as a fuse in which thematerial may be heated to a temperature resulting, at least in part, ina rupture of the device that may not be easily reversed. In animplementation, a PCM material comprising a rupture may exhibit a higherresistance state.

Embodiments of claimed subject matter may involve an “offset” distance,which may, for example, pertain to a distance from a point directlyabove an active portion of a memory material to an edge of a conductivematerial. Embodiments of claimed subject matter may involve anapplicable “lithographic pitch,” which may correspond to a width of thenarrowest parallel lines or the narrowest parallel spaces that may beformed employing a lithographic tool or process. However, these aremerely examples, and claimed subject matter is not limited in thisrespect.

FIG. 1 shows at least a portion of a memory device (105) according toone embodiment of claimed subject matter. In FIG. 1, an application ofprogramming voltage, Vp, may generate an electrical current inelectrical conductor 100 that may flow from Vp to edge 101. In anembodiment, a programming voltage may comprise approximately 1V,although nothing prevents use of programming voltages having a greatermagnitude, such as 3V to 5V, or having a lesser magnitude, such as 500mV or 100 mV. Of course, these are non-limiting examples. Additionally,conductor 100 may comprise a conductive material, such as copper,although nothing prevents use of other conductive materials, such asaluminum, that may be capable of conveying an electrical current. Again,these are non-limiting examples.

In at least one embodiment, active material 120, for example, mayinclude a chalcogenide PCM material. A PCM material may includegermanium (Ge), antimony (Sb), and tellurium (Te), such as Ge₂Sb₂Te₅,for example, which may undergo a phase change at least partially as afunction of heat applied, for example. Active material 120 may alsoinclude materials such as Gold (Ag), Indium (In), Sb, and Te, such asAgInSbTe, InSe, SbSe, SbTe, InSbSe, SbTe, or combinations thereof,and/or any other material capable of storing information by way of aphase change that may be affected at least partially by applying thermalenergy.

Separation material 110 may be disposed under, such as beneath,conductor 100 or may be immediately adjacent conductor 100. Separationmaterial 110 may be applied to reduce or eliminate a likelihood thatmaterials in a semiconductor structure, such as illustrated in FIG. 1,might migrate across 110, including from a first side of material 110 toa second side of material 110. In FIG. 1, separation material 110 mayintervene to act as a diffusion barrier that may reduce electromigrationbetween conductor 100, which may be disposed over or included onmaterial 110, and active material 120, which may be disposed below orimmediately to adjacent material 110.

Separation material 110 may comprise a refractory metal, such as atitanium alloy or other compound, such as titanium/titanium nitride,tungsten, titanium/tungsten alloy, chromium, tantalum, or their alloys,to provide non-limiting examples. In at least one embodiment, such asFIG. 1, material 110 may comprise approximately 40 to 60 nm in thicknessand may include a titanium nitride material of approximately 15-30 nmand a tungsten material of approximately 20-40 nm. However, nothingprevents using other materials and/or materials having thicknesseswithin different ranges. Claimed subject matter is not limited to use ofparticular materials and/or thicknesses.

As mentioned previously, active material 120 may be disposed under, suchas beneath, separation material 110. In a largely resistive phase, whichmay result from heating a memory material beyond a phase changetemperature for a short period of time, for example, a materialcomprising active material 120 may transition to an amorphous phase, forexample. In a largely conductive phase, which may result from heating amaterial to a lower temperature than above and for a longer period oftime, a material may transition to a crystalline phase. Further, anamorphous or a crystalline phase of a material may persist for anextended period of time after a heat source is removed from contact withthe material. Resistance, such as to a current passing through a memorymaterial, may be observed by way of measuring a drop in voltage signallevel across contacts of a device. Resistance may be used to store astate, such as one or more binary digits that may represent one or moreinformation states.

In at least one embodiment, device heater 140 may be disposed under,such as beneath, active material 120 and at least partially embeddedwithin or surrounded by dielectric material 130. In FIG. 1, deviceheater 140 may, for example, comprise an “L” shape and may comprisetitanium nitride, titanium nitride doped with silicon, and/or other typeof titanium nitride composite, for example. In other embodiments, deviceheater 140 may assume other shapes or include other types of materialsthat may exhibit heating properties at least partially in response to anelectrical current; however claimed subject matter is not necessarily solimited.

Dielectric material 130 may partially or fully surround device heater140 and may include an insulating dielectric oxide or nitride that maypossess electrical and thermal insulation properties. Dielectricmaterial 160 may also include an oxide or nitride that may possesselectrical and/or thermal insulation properties. In an embodiment inwhich dielectric material 130 and 160 comprise Silicon Nitride (Si₃N₄),for example, materials 130 and 160 may exhibit a resistivity within arange of approximately 10¹² ohm-cm to 10¹⁶ ohm-cm and a thermalconductivity in the range of approximately 20 W/m° K to 40 W/m° K.However, claimed subject matter is not necessarily so limited.

A conductive plug 150 may be disposed under, such as beneath, deviceheater 140. In at least one embodiment, conductive plug 150 may becoupled to a switch 170. Although shown as a metal oxide semiconductortransistor, other types of switches and/or switching elements may, ofcourse, be used. In at least one embodiment, an N-channel metal oxidesemiconductor transistor (NMOS) may be employed and may include, amongother features, an ability to generate reverse bias polarity. However,claimed subject matter is not limited in this respect.

FIG. 1A shows at least a portion of a memory device (105A) havingsimilarities with the embodiment of FIG. 1. In FIG. 1A, switch 170A,implemented by way of an NMOS transistor, may have a configuration witha drain in contact with conductor 100A. Accordingly, current may flowfrom Vp through conductive plug 150A, device heater 140A, activematerial 120A, separation material 110A, conductor 100A, and throughswitch 170A to ground, for example. In an implementation, activematerial 120A may be heated beyond a temperature at which one or more ofmaterial 120A, device heater 140A, and/or conductive plug 150A undergoesa rupture, for example, and may exhibit higher resistivity. In animplementation, if device 105A undergoes a rupture, the device may notbe easily returned to a lower resistance state.

FIG. 2 shows the embodiment of FIG. 1 with an electrical current flowingas described below. In at least one embodiment, a relative thickness, F,of separation material 210 with respect to a lateral distance 202, suchas 2F, is shown. Material 210 may extend beyond or be offset from edge201 of conductor 200 to a location at least approximately directly abovedevice heater 240. In FIG. 2, F may indicate a dimension approximatelyequal to one-half of a pitch of an applicable lithographic process usedto lay out memory device 205, for example. In one example, in which a100 nm lithographic process may be used, a lateral distance may compriseapproximately 100 nm.

Other embodiments of claimed subject matter may employ otherlithographic processes, including some with different pitches providinga different or offset lateral distance. In other embodiments, a materialthickness and a lateral distance that separation material 110 extendsbeyond edge 101 of conductor 100 to a point directly above device heater140 need not be precisely related by a ratio of F:2F. Alternatively,they may be related in another manner. For example, they may be relatedby a ratio of F:F, in which a material thickness and a lateral distancemay be approximately equal. In another embodiment, these may be relatedby a different ratio, such as F:3F. In other embodiments, thickness andlateral distance may not even be related by way of a ratio. However,these are merely examples, and claimed subject matter is not limited inthis respect.

In FIG. 2, direction of an electrical current may be shown originatingat Vp and terminating at electrical ground. Accordingly, a currentapplied from Vp may travel laterally across conductor 200, for example,which may comprise copper, aluminum, or other conductive material, untilapproximately reaching edge 201. After reaching edge 201, current maytravel through a portion of material 210, as illustrated by example.Such path may be a path of lesser or least resistance; however, theembodiments are not so limited. Current may travel through portion 225of active material 220 to a top portion of device heater 240 withindielectric material 230. After passing through device heater 140,current may travel through conductive plug 250 and through switch 270.

One or more embodiments may make use of a separation material thatcomprises a titanium alloy or a compound such as titanium/titaniumnitride, tungsten, titanium/tungsten alloy, chromium, tantalum, and/ortheir alloys, to provide a diffusion barrier, such as anelectromigration barrier, between a conductor and an active material.For example, a portion of a separation material 210 may introduce aresistance per unit length larger than a resistance per unit length of aconductor. In an embodiment, for example, in which material 210 maycomprise tungsten nitride having a sheet resistance of 300 to 400micro-ohms/square, a portion of material 210 may comprise a material oflesser resistance, such as approximately 50 ohms to 150 ohms.

In other embodiments, different constituent elements may be used formaterial 210, and/or material 210 may be thicker, such as for example,1.6F (approximately 80 nm), or a portion of material 210 may be shorterin length, for example 0.8F (approximately 40 nm). In these embodiments,material 210 may introduce smaller resistance, such as about 40 ohms orless. In other embodiments, which may involve use of differentconstituent elements for material 210, or in which material 210 may bethinner, such as for example, 0.6F (approximately 30 nm), or in whichmaterial 210 is of a greater length, for example 3F (approximately 150nm), material 210 may introduce greater resistance, such as about 150ohms, about 200 ohms, about 300 ohms, or more. However, these are merelyexamples, and claimed subject matter is not limited in this respect.

After passing through material 210, current may continue through activematerial 220. A memory material that may be transitioned from a largelyresistive phase to a largely conductive phase may comprise activematerial 220. Such a transition from crystalline to amorphous or fromamorphous to crystalline may allow a memory material to store a state asone or more encoded binary digits according to a resistive phase of amemory material, for example. A material may be included within activematerial 220 in various states through a variety of technologies as aresult of a manufacturing process used to fabricate a device structure.Accordingly, an electrical current flowing through portion 225 of activematerial 220 may reach a top portion of device heater 240 without activematerial 220 introducing significant resistance.

As an electrical current may continue through device heater 240, Joule,resistive, or ohmic heating of device heater 240 may result. As a resultof device heater 240 increasing in temperature, portion 225 of activematerial 220, near a top portion of device heater 240 may undergoheating as well. As portion 225 of active material 220 heats, memorymaterial of portion 225 may change from a crystalline phase to anamorphous phase. In at least one embodiment, for example, an electricalcurrent may function to program portion 225 of active material 220, suchas by way of device heater 240. After continuing through device heater240, electrical current may be applied to conductive plug 250, via aswitching device 270, and to electrical ground.

In FIG. 2, it can be seen that edge 201 of conductor 200 is offset froma point directly above portion 225 of active material 220 by an amountapproximately equal to 2F. In an embodiment, locating edge 201 away froma point directly above portion 225 may result in a small amount, or evena negligible amount, of heat from portion 225 conducting to conductor200. Accordingly, if conductor 200 comprises a material that may bethermally conductive as well as electrically conductive, although heatfrom portion 225 may affect conductor 200, locating conductor 200 awayfrom a point directly above portion 225 may desirably reduce coupling ofthermal energy from portion 225 to conductor 200. In one embodiment, forexample, an ability to reduce coupling of thermal energy from portion225 to conductor 200 may result in an ability to reduce a current thatmay be used to program portion 225. Reducing a current that may be usedin programming portion 225 may contribute to a decrease in failures thatresult, at least in part, from excess current used in programming.

In an embodiment, if an edge, such as edge 201 of conductor 200, isoffset by a larger distance from a point directly above portion 225 ofactive material 220, such as a distance of about 3F, or greater,resistance resulting from electric current flow through separationmaterial 210 may be expected to increase. Thus, for example, ifconductor 200 were offset by a distance of about 3F (approximately 150nm), for example, an additional resistance may result. Assuming atypical resistivity, approximately 50 ohms of additional resistance mayresult. In another example, if conductor 200 were offset a distance ofabout 4F (approximately 200 nm) an additional resistance of perhaps 100ohms may result. Accordingly, an offset design trade-off may be made,which may result in a decrease in conduction of heat energy from portion225 to conductor 200, for example. However, in the event that conductor200 is offset a greater distance, separation material may exhibit anadditional resistance.

In an embodiment, in which Vp may be set to approximately 1V during aprogramming operation of portion 225 of active material 220, as anillustrative example, a voltage drop resulting from separation material210 may approximate about 100 mV. In other embodiments, if programmingportion 225 of active material 220, it may be desirable for separationmaterial 210 to exhibit smaller voltage drops, such as about 50 mV orless, for example. In embodiments, a smaller offset of edge 201 fromportion 225, such as F, may approximate about 50 nm. In otherembodiments, larger voltage drops resulting from separation material 210may be tolerated, such as about 200 mV or more. However, these aremerely examples, and claimed subject matter is not limited in thisrespect.

FIG. 2A shows electrical current flow through the embodiment of FIG. 1A.In an implementation, device heater 240A may heat portion 225A of activematerial 220A to a temperature beyond the temperature at which one ormore of portion 225A, device heater 240, and/or conductive plug 250 mayrupture, for example. In an implementation, current may flow from Vpthrough conductive plug 250A, device heater 240A, portion 225A of activematerial 220A, separation material 210A, conductor 200A, and throughswitch 270A to ground, for example. In an implementation, if a portionof device 205A undergoes a rupture, the device may not be easilyreturned to a lower resistance state.

FIG. 3 shows a diagram (300) of circuit elements that may represent acircuit embodiment of FIG. 1. In FIG. 3, Vp may represent a voltagesource applied to a conductive path such as previously described, forexample. A voltage signal from Vp may be conveyed through R₃₀₀, whichmay represent a resistance of a conductive path to which an electricalcurrent from Vp may be applied such as previously described, forexample. A value for R₃₀₀ may be small, such as from about 10 ohms orless.

Current from R₃₀₀ may flow through R₃₁₀, which may represent aresistance resulting from a separation material, such as material 110and 210 of FIGS. 1 and 2, for example. Material 110 and 210 mayrepresent a resistance of perhaps about 50 ohms or less to a valueperhaps as high as about 500 ohms or more. R₃₁₀ may be contemplated asbeing in a region of about 100 ohms, although claimed subject matter isnot limited in this respect.

Current from R₃₁₀ may continue to R₃₂₅, which may represent a portion ofa PCM material programmed by an electrical current. An electricalcurrent may flow through memory portion 125 or 225, represented by R₃₂₅,to a device heater, represented by R₃₄₀. In the embodiment of FIG. 3,the R₃₄₀ may perhaps be larger than R₃₀₀, R₃₁₀, or R₃₂₅. Accordingly,current flow through R₃₄₀ may result in an increase in a temperature ofa device heater, represented by R₃₄₀, which may raise a temperature of aportion of a PCM material to a value beyond a melting point. Therefore,a portion of a phase change material may store one or more informationstates. Current may be returned to a negative terminal of Vp by way ofswitching device 370.

FIG. 4 shows a flow chart for at least a portion of a method of making amemory device according to an embodiment. In some embodiments, theapparatus of FIG. 1 may be suitable for performing the method of FIG. 4,although nothing prevents performing the method of FIG. 4 usingalternate arrangements of components in other embodiments. Embodimentsmay include additional blocks than those shown and described in FIG. 4,fewer blocks, blocks occurring in an order different from FIG. 4, or anycombination thereof.

FIG. 4 begins at block 400, which may include disposing a PCM material,such as a portion of a chalcogenide glass active material, over or on adevice heater. Block 400 may include depositing a dielectric materialthat at least partially surrounds a device heater comprising titaniumnitride, titanium nitride doped with silicon, or other type of titaniumnitride composite. In block 400, a dielectric material may include, forexample, an insulating dielectric oxide or nitride that possessessuitable electrical and/or thermal insulation properties.

Continuing at block 410, in which a separation material may be disposedover, including on, a memory device, perhaps, for example, in whichabout a 20 nm film of titanium nitride may be deposited or sputteredfollowed by about a 30 nm tungsten film deposited in a similar manner,for example. A separation material introduced at block 410 may possessan electrical resistance of about 5% to about 10%, for example, of aresistance exhibited by a device heater disposed at block 410. However,in some embodiments, a separation material may introduce a largerelectrical resistance, which may be as high as about 50% or more of aresistance exhibited by a device heater in other examples.

Continuing, block 420 may include at least partially removing aconductor, typically in the form of a conductor material over aseparation material, in which a conductor includes an edge that may beoffset from a point directly above a PCM material, for example. In anembodiment, a small or negligible amount of heat generated by a deviceheater may conduct away from the device heater. In one embodiment, block420, may include the use of a damascene process to fabricate aconductive path followed by chemical mechanical planarization. However,claimed subject matter is not limited in this respect.

FIG. 5 shows a flow chart for at least portion of a method of operatinga memory device according to an embodiment. In some embodiments, theapparatus of FIG. 1 may be suitable for performing the method of FIG. 5,although nothing prevents performing the method of FIG. 5 usingalternate arrangements of components in other embodiments. Embodimentsof claimed subject matter include additional blocks than those shown anddescribed in FIG. 5, fewer blocks, blocks occurring in an orderdifferent from FIG. 5, or any combination thereof

Block 500 describes that a current may be applied to a first conductor.At block 510, a current path may form from a first conductor by way ofan intervening separation material. At block 510, a separation materialmay include titanium nitride, tungsten, or other metals or compounds,arranged in any combination, so as to reduce, including eliminate,diffusion, including electromigration, between portions above andportions below as a result.

Depicted at 520 a PCM material may attain a temperature that results ina phase change. A device heater may comprise titanium nitride, titaniumnitride doped with silicon, or may be any other conductive or partiallyconductive material capable of converting an electrical current intoheat energy by way of ohmic, resistive, or Joule heating, for example. Avoltage drop exhibited by a first conductor may be less than a voltagedrop exhibited by an intervening separation material. Further, a voltagedrop exhibited by a device heater may represent a voltage drop largerthan a voltage drop exhibited by an intervening separation material.

In some circumstances, operation of a memory device, such as a change instate from a binary one to a binary zero or vice-versa, for example, maycomprise a transformation, such as a physical transformation. Withparticular types of memory devices, such a physical transformation maycomprise a physical transformation of an article to a different state orthing. For example, but without limitation, for some types of memorydevices, a change in state may involve an accumulation and storage ofcharge or a release of stored charge. Likewise, in other memory devices,a change of state may comprise a physical change or transformation inmagnetic orientation or a physical change or transformation in molecularstructure, such as from crystalline to amorphous or vice-versa. In stillother memory devices, a change in physical state may involve quantummechanical phenomena, such as, superposition, entanglement, or the like,which may involve quantum bits (qubits), for example. The foregoing isnot intended to be an exhaustive list of all examples in which a changein state for a binary one to a binary zero or vice-versa in a memorydevice may comprise a transformation, such as a physical transformation.Rather, the foregoing are intended as illustrative examples.

A computer-readable (storage) medium typically may be non-transitory orcomprise a non-transitory device. In this context, a non-transitorystorage medium may include a device that is tangible, meaning that thedevice has a concrete physical form, although the device may change itsphysical state. Thus, for example, non-transitory refers to a deviceremaining tangible despite this change in state.

The terms, “and”, “or”, and “and/or” as used herein may include avariety of meanings that also are expected to depend at least in partupon the context in which such terms are used. Typically, “or” if usedto associate a list, such as A, B or C, is intended to mean A, B, and C,here used in the inclusive sense, as well as A, B or C, here used in theexclusive sense. In addition, the term “one or more” as used herein maybe used to describe any feature, structure, or characteristic in thesingular or may be used to describe a plurality or some othercombination of features, structures or characteristics. However, itshould be noted that this is merely an illustrative example and claimedsubject matter is not limited to this example.

Methodologies described herein may be implemented by various approachesdepending, at least in part, on applications according to particularfeatures or examples. For example, such methodologies may be implementedin hardware, firmware, or combinations thereof, along with software. Ina hardware implementation, for example, a processing unit may beimplemented within one or more application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), processors, controllers, microcontrollers,microprocessors, electronic devices, other devices units designed toperform the functions described herein, or combinations thereof.

In the preceding detailed description, numerous specific details havebeen set forth to provide a thorough understanding of claimed subjectmatter. However, it will be understood by those skilled in the art thatclaimed subject matter may be practiced without these specific details.In other instances, methods or devices that would be known by one ofordinary skill have not been described in detail so as not to obscureclaimed subject matter.

While there has been illustrated and described what are presentlyconsidered to be example features, it will be understood by thoseskilled in the art that various other modifications may be made, andequivalents may be substituted, without departing from claimed subjectmatter. Additionally, many modifications may be made to adapt aparticular situation to the teachings of claimed subject matter withoutdeparting from the central concept described herein. Therefore, it isintended that claimed subject matter not be limited to the particularexamples disclosed, but that such claimed subject matter may alsoinclude all aspects falling within the scope of appended claims, andequivalents thereof.

What is claimed is:
 1. An apparatus, comprising: a memory materialhaving a first edge and a second edge that is laterally offset from thefirst edge in a first direction; a separation material positioned overthe memory material and having a first edge and a second edge that islaterally offset from the first edge in the first direction; and aconductive material positioned over the separation material and having afirst edge and a second edge that is laterally offset from the firstedge in the first direction, wherein the second edge of the separationmaterial and the second edge of the memory material extend farther inthe first direction than the second edge of the conductive material. 2.The apparatus of claim 1, wherein the memory material comprises aprogrammable portion, and wherein the second edge of the conductivematerial is laterally offset from a center of the programmable portionof the memory material in a second direction by a distance that isgreater than or equal to a height of the separation material, the seconddirection being different than the first direction.
 3. The apparatus ofclaim 1, wherein the first edge of the separation material and the firstedge of the conductive material are aligned, and wherein the second edgeof the conductive material is laterally offset from the second edge ofthe separation material in a second direction that is different than thefirst direction.
 4. The apparatus of claim 1, wherein the first edge ofthe memory material is aligned with the first edge of the conductivematerial and the second edge of the memory material is aligned with thesecond edge of the separation material.
 5. The apparatus of claim 1,wherein: the memory material comprises a programmable portion, theconductive material is non-overlapping with the programmable portion ofthe memory material in the first direction, and the separation materialis overlapping with at least a portion the programmable portion in thefirst direction.
 6. The apparatus of claim 1, further comprising: adielectric material positioned below the memory material, the dielectricmaterial comprising a resistive material that is positioned below and incontact with a programmable portion of the memory material.
 7. Theapparatus of claim 6, wherein: the resistive material comprisestitanium, titanium nitride, tungsten, tungsten nitride, chromium, ortantalum, or any combination thereof, the separation material comprisestitanium, titanium nitride, tungsten, chromium, tantalum, or anycombination thereof, and the conductive material comprises copper, oraluminum, or any combination thereof.
 8. The apparatus of claim 1,further comprising: a conductive plug positioned below the memorymaterial; and a switching device positioned below the conductive plugand coupled with a ground reference.
 9. A method of forming anapparatus, comprising: forming a memory material having a first edge anda second edge that is laterally offset form the first edge in a firstdirection; forming, over the memory material, a separation materialhaving a first edge and a second edge that is laterally offset from thefirst edge in the first direction; and forming, over the separationmaterial, a conductive material having a first edge and a second edgethat is laterally offset from the first edge in the first direction,wherein the second edge of the separation material and the second edgeof the memory material extend farther in the first direction than thesecond edge of the conductive material.
 10. The method of claim 9,further comprising: forming a resistive material, wherein the memorymaterial is formed over the resistive material; and forming a dielectricmaterial that at least partially surrounds the resistive material. 11.The method of claim 9, wherein forming the conductive material comprisesremoving a portion of the conductive material that lies above aprogrammable portion of the memory material.
 12. The method of claim 9,further comprising: forming a conductive path across the memorymaterial, the separation material, and the conductive material.
 13. Themethod of claim 10, further comprising: forming a conductive plug,wherein the resistive material is formed over the conductive plug; andforming a switching device, wherein the conductive plug is formed overthe switching device.
 14. The method of claim 10, wherein: the resistivematerial comprises titanium, titanium nitride, tungsten, tungstennitride, chromium, or tantalum, or any combination thereof, theseparation material comprises titanium, titanium nitride, tungsten,chromium, tantalum, or any combination thereof, and the conductivematerial comprises copper, or aluminum, or any combination thereof. 15.The method of claim 9, wherein the memory material comprises aprogrammable portion, and wherein the second edge of the conductivematerial is laterally offset from a center of the programmable portionof the memory material in a second direction by a distance that isgreater than or equal to a height of the separation material, the seconddirection being different than the first direction.
 16. The method ofclaim 9, wherein the first edge of the separation material and the firstedge of the conductive material are aligned, and wherein the second edgeof the conductive material is laterally offset from the second edge ofthe separation material in a second direction that is different than thefirst direction.
 17. The method of claim 9, wherein the first edge ofthe memory material is aligned with the first edge of the conductivematerial and the second edge of the memory material is aligned with thesecond edge of the separation material.
 18. The method of claim 9,wherein: the memory material comprises a programmable portion, theconductive material is non-overlapping with the programmable portion ofthe memory material in the first direction, and the separation materialis overlapping with at least a portion the programmable portion in thefirst direction.